At gasoline service stations, gasoline is stored in large, underground tanks and is pumped from the tanks to above ground dispensers from which the gasoline is dispensed. Submersible pumps are normally used to carry out the pumping operation. In this type of application and in other pumping applications, it is common for the liquid which is being pumped to contain particulate matter. Screen type filters are often provided at the dispensing station in order to prevent the particles from being dispensed along with the gasoline. However, the provision of filters at the dispenser is not an entirely satisfactory solution. The filters can become clogged and must be cleaned and/or replaced at frequent intervals. Also, the particulate matter that passes through the pump can cause damage to bearings and other pump components and thus decrease the useful life of the pump.
It has been proposed to provide inlet strainers on pumps of various types in order to prevent particulate materials from reaching the pump inlet port. In addition to preventing damage to the pump and reducing the maintenance requirements of the dispenser, the use of a pump inlet strainer has the further advantage of allowing back washing of the particulate matter when the pump is not operating.